Current space cooling technologies employ an electric motor (dc or ac) to turn a set of blades that are inclined to their plane of rotation. The movement of inclined blades impinging on the column of stationary air provides pressurized air movement towards an object/person or surface to induce cooling by natural evaporation. These fan technologies can be ceiling-mounted, wall-mounted or standing, and air-flow is controlled by controlling speed of the motor. For wall-mounted and standing fans, air-flow direction can be oscillated by using another motor or reduction gear train to rotate the main motor blade assembly. However, ceiling-mounted units have fixed air-flow direction and air is directed from the top, i.e., the ceiling, to a user sitting below. Such bladed ceiling fans and wall-mounted fans have serious drawbacks and one of the disadvantages is the pushing of hot air from the ceiling to the user below. This technology has not changed since its invention some hundred years ago. This type of air movement is very energy inefficient aerodynamically.
Recent development in fan technology has resulted in a ‘No Visible Blades” fan invented by Sir James Dyson and being sold under the same name. The Dyson fan with a blower concealed in the circular body of its stand forces pressurized air through an annulus slit near the leading edge of an aerofoil surface to draw secondary air. This type of fan has the advantage that it is perceived as ‘Bladeless’ and safe. Being a new product based on a novel concept, it is currently very expensive and comes as a standing fan design. The novelties are the use of the aerofoil to draw secondary air amplifying the total air-flow and the concealed blades design.